1. Field of the Invention
This invention relates to image processing, more particularly to image processing for graphics images.
2. Background of the Invention
Graphics data comes in several formats, such as VGA, SVGA, XGA, SXGA, etc., each with a different spatial resolution. For example, VGA has a 640.times.480 resolution. A problem arises when graphics data of one format and resolution needs to be resized to fit a display system with a different resolution. For example, an image that was formatted for VGA at 640.times.480 resolution may need to be displayed on a 800.times.600 resolution display system. This type of problem is becoming more and more prevalent as more options are offered to consumers for display systems.
Graphics data, unlike incoming video data, cannot be resized horizontally by changing the sampling frequency. In the above example, if the input were analog video data, the sampling frequency for that display system would be 800 samples per line instead of 640. Graphics data, however, is originally created in a digital fashion. This results in a signal that is only stable in discrete portions of the analog signal.
A typical solution to this problem is to scale the data digitally, in both the horizontal and vertical directions. In the above example, the 640 samples per line must be scaled to result in 800 samples per line, and the 480 lines must be scaled to result in 600 lines. Additionally, just as graphics data is scaled up from 640.times.480 to 800.times.600, it can also be scaled down. These scaling operation are typically performed by a programmable video processor, such as the Scan-line Video Processor (SVP) manufactured by Texas Instruments, or processing chips such as the Genesis 833.
Due to cost and real-time processing restraints, scaled images such as that discussed above, appear blurry or soft due to the use of a low-complexity scaling implementation. Graphics images have a tendency to have sharp edges, which become noticeably blurred.
Therefore, a method for enhancing image sharpness for resized graphics is needed.